Conventional liquid filled plastic bottles which utilize a threaded plastic cap have typically had problems with leaking. Seals such as plug seals and conventional gaskets are known and reduce the problem; however, neither plug seals nor conventional gaskets provide a leak free seal when using closures that are twisted to a particular position and not a specific torque. As a result, conventional plug seals and gaskets will leak when rocked or wobbled. Typically, rocking the bottle to one side will cause the seal on the opposite side to be broken. As a result, the plug seal and gasket will leak.
Another problem with using conventional gaskets to alleviate the problem with leaking is that the gasket increases the complexity of the design and the cost. In addition, if the gasket is not aligned properly, the leaking problem will actually be increased.
Therefore, what is needed is a seal which is leak free regardless of rocking or wobbling of the bottle.